canvas: Use snapshot in canvas backends (#37863)

This removes assumption about pixel format from backend abstraction to
actual backend implementation. This is important for vello.

Testing: WPT tests

---------

Signed-off-by: sagudev <16504129+sagudev@users.noreply.github.com>

components/script/canvas_state.rs

@@ -1186,14 +1186,7 @@ impl CanvasState {
             let size = snapshot.size();
             Ok(Some(CanvasPattern::new(
                 global,
-                snapshot
-                    .to_vec(
-                        Some(SnapshotAlphaMode::Transparent {
-                            premultiplied: true,
-                        }),
-                        Some(SnapshotPixelFormat::BGRA),
-                    )
-                    .0, // TODO: send snapshot
+                snapshot,
                 size.cast(),
                 rep,
                 self.is_origin_clean(image),
@@ -1703,10 +1696,8 @@ impl CanvasState {
         };
 
         // Step 7.
-        let (sender, receiver) = ipc::bytes_channel().unwrap();
-        let pixels = unsafe { &imagedata.get_rect(Rect::new(src_rect.origin, dst_rect.size)) };
-        self.send_canvas_2d_msg(Canvas2dMsg::PutImageData(dst_rect, receiver));
-        sender.send(pixels).unwrap();
+        let snapshot = imagedata.get_snapshot_rect(Rect::new(src_rect.origin, dst_rect.size));
+        self.send_canvas_2d_msg(Canvas2dMsg::PutImageData(dst_rect, snapshot.as_ipc()));
     }
 
     // https://html.spec.whatwg.org/multipage/#dom-context-2d-drawimage

components/script/dom/canvaspattern.rs

@@ -5,6 +5,7 @@
 use canvas_traits::canvas::{FillOrStrokeStyle, RepetitionStyle, SurfaceStyle};
 use dom_struct::dom_struct;
 use euclid::default::{Size2D, Transform2D};
+use pixels::{IpcSnapshot, Snapshot};
 
 use crate::dom::bindings::cell::DomRefCell;
 use crate::dom::bindings::codegen::Bindings::CanvasRenderingContext2DBinding::CanvasPatternMethods;
@@ -21,7 +22,8 @@ use crate::script_runtime::CanGc;
 #[dom_struct]
 pub(crate) struct CanvasPattern {
     reflector_: Reflector,
-    surface_data: Vec<u8>,
+    #[no_trace]
+    surface_data: IpcSnapshot,
     #[no_trace]
     surface_size: Size2D<u32>,
     repeat_x: bool,
@@ -33,7 +35,7 @@ pub(crate) struct CanvasPattern {
 
 impl CanvasPattern {
     fn new_inherited(
-        surface_data: Vec<u8>,
+        surface_data: Snapshot,
         surface_size: Size2D<u32>,
         repeat: RepetitionStyle,
         origin_clean: bool,
@@ -47,7 +49,7 @@ impl CanvasPattern {
 
         CanvasPattern {
             reflector_: Reflector::new(),
-            surface_data,
+            surface_data: surface_data.as_ipc(),
             surface_size,
             repeat_x: x,
             repeat_y: y,
@@ -57,7 +59,7 @@ impl CanvasPattern {
     }
     pub(crate) fn new(
         global: &GlobalScope,
-        surface_data: Vec<u8>,
+        surface_data: Snapshot,
         surface_size: Size2D<u32>,
         repeat: RepetitionStyle,
         origin_clean: bool,

components/script/dom/imagedata.rs

@@ -12,6 +12,7 @@ use js::gc::CustomAutoRooterGuard;
 use js::jsapi::JSObject;
 use js::rust::HandleObject;
 use js::typedarray::{ClampedU8, Uint8ClampedArray};
+use pixels::{Snapshot, SnapshotAlphaMode, SnapshotPixelFormat};
 
 use super::bindings::buffer_source::{HeapBufferSource, create_heap_buffer_source_with_length};
 use crate::dom::bindings::buffer_source::create_buffer_source;
@@ -183,6 +184,18 @@ impl ImageData {
         pixels::rgba8_get_rect(unsafe { self.as_slice() }, self.get_size().to_u32(), rect)
     }
 
+    #[allow(unsafe_code)]
+    pub(crate) fn get_snapshot_rect(&self, rect: Rect<u32>) -> Snapshot {
+        Snapshot::from_vec(
+            rect.size,
+            SnapshotPixelFormat::RGBA,
+            SnapshotAlphaMode::Transparent {
+                premultiplied: false,
+            },
+            unsafe { self.get_rect(rect).into_owned() },
+        )
+    }
+
     #[allow(unsafe_code)]
     pub(crate) fn to_shared_memory(&self) -> IpcSharedMemory {
         // This is safe because we copy the slice content